Many conditions and diseases are associated with abnormalities of a surface. The existence and severity of the condition can be diagnosed by plotting data measurements of thickness of the surface layer, that is, height from a chosen base layer and comparing the results to a normal surface, that is, one that is not diseased. These conditions may include coronary artery disease, abnormal angiogenesis as in diabetic retinopathy and blood vessel thrombi. The eye disease glaucoma, a leading cause of blindness, is characterized by alterations in the retinal nerve fiber layer.
It is well known that the necessary point measurements can be obtained by scanning laser polarimetry (SLP), ocular coherence tomography (OCT), ultrasound, photogrammetry or the like. However, the reliability and power of such methods are dependant on the mathematical analysis of the data. Some previous methods selected a normal value for the thickness of the surface in question and determined individual variations from normal values.